S-II mediated gene regulation.

S-II, also designated as TFIIS, was the first identified transcription elongation factor and is widely found in eukaryotes. Among known elongation factors, S-II has a characteristic biochemical activity: it facilitates the elongation process by allowing RNA polymerase II (RNAPII) to read through transcriptional blocks in vitro. While the biochemical and molecular mechanism of stimulating elongation in vitro has been shown in detail, the in vivo role of S-II long remained unclear. Recent research has revealed that S-II has a crucial role in the activation of expression of a set of genes in vivo. In this review, we summarize recent studies focusing on the regulation of gene expression by S-II and discuss the biological functions of S-II.